Complicated Piping Research Articles

Virtual design on the heat pump refrigeration cycle: challenges and approaches

Virtual product design (VPD) of the refrigeration cycle has long been a major subject of many engineers and manufacturers. Issues should be the question of how simulation gets close to the real world in virtual ways. It is especially true when we consider variable refrigerant flow (VRF) heat pumps, having various types of indoor unit combinations, long and complicated piping configurations, and simultaneous cooling and heating functions under extreme weather conditions. In this regard, model-based systems engineering (MBSE) or model-based design (MBD) guides a methodology to make a virtual model easily. Now, there are plenty of engineering platforms and tools to make a strong simulation model, which provides interfacing technology among multiple physics, different dimensions, and codes in different languages. In the study, the authors share their experience in the virtual design for a VRF heat pump system including the architecture, multiple physics, and the connection with the control SW. Modelica, an acausal and object-oriented modeling language, constructs the backbone of the model to describe the dynamic behavior of refrigerants and to combine external components in the form of functional mock-up units (FMUs). The developed virtual model is validated against measured data, showing it can reproduce all the essential physics of interest both in qualitative and quantitative ways.

Development of inverted pendulum thrust stand with spring-shaped wire for high power electric thrusters.

Pendulum thrust stands are used to measure the thrust of electric propulsion systems for spacecraft. A thruster is mounted on a pendulum and operated, and the pendulum displacement due to thrust is measured. In this type of measurement, the pendulum is also affected by nonlinear tensions due to wiring and piping that deteriorate the accuracy of the measurement. This influence cannot be ignored in high power electric propulsion systems because complicated piping and thick wirings are required. Therefore, to reduce the influence of tension due to wires and tubes, we developed an inverted pendulum-type thrust stand with pipes and wirings as springs. In this paper, we first derive the design guidelines for spring-shaped wires; the necessary conditions for sensitivity, responsivity, spring shape, and electric wire were formulated. Next, a thrust stand was designed and fabricated based on these guidelines, and the performance of the stand was evaluated through calibration and thrust measurements using a 1 kW-class magneto-plasma-dynamics thruster. The sensitivity of the thrust stand was 17 mN/V, the normalized standard deviation of the variation of the measured values owing to the structure of the thrust stand was 1.8 × 10-3, and the thermal drift during the long-time operation was ∼4.5 × 10-3 mN/s.

자동격자생성 알고리듬을 이용한 주름관을 갖는 배관계의 효율적 진동 분석

In this study, an automatic mesh generation algorithm was developed for efficient finite shell element modeling of piping systems with bellows. For pre-processing of finite element analysis, a pipe geometry should be modeled using meshing software. However, the finite element meshing process requires time-consuming efforts for complicated piping systems such as bellows. Therefore, this study proposed an algorithm that can efficiently generate finite shell elements automatically. To generate the finite shell element model of the pipe, this algorithm only needs the information of the centerline of the pipe and the corresponding radius that is identical to the finite beam element. Additionally, effects of bellows on the dynamic characteristics of a curved pipe were discussed. The variation of the natural frequencies and dynamic stiffness of the piping system with respect to the change of the location, height and width of the bellows were investigated. The suggested automatic mesh algorithm is advantageous for the modeling of pipes having complex shapes such as bellows. Hence, it has the potential to be useful in designing optimal bellows in piping systems that require numerous finite element analysis calculations.

부생가스 연료배관의 설계변경에 따른 안전성 평가

Various process piping usually carries out high flammable and explosible gas under high pressure and high temperature. Due to frequent change of design and structure it becomes more complicated and compactly located. The safety management level is relatively low since it is considered as simply designed component. In this study a safety assessment procedure is proposed for complicated piping system around a mixing drum in which natural gas and by-product gases were mixed. According to ASME code, pipe stress analysis was conducted for determining design margin at some key locations of the piping. These high stress locations can be used as major inspection points for managing the pipe integrity. Sensitivity analysis with outside temperature of the pipe and support constraint condition. Possible effect of hydroen gas to the pipe steel during the previous use of the by-product gas was also discussed.

Comparison between the effects of ultrasonic and thermal stimulation on release of internal hydrophobic dyes from Pluronic micelles

In this study, we propose a novel chemical reaction process using Pluronic micelles as reactant carriers in order to reduce complicated piping. A Pluronic micelle containing the hydrophobic dye NKX-1595 was prepared by a dialysis method, and the release of the internal dye from the micelle by external stimulation was investigated. In particular, we investigated the effects of the combination of ultrasonic frequency and type of Pluronic on degree of dye release (DDR). A low ultrasonic frequency is effective for the release of the internal dye from the micelle and ultrasonic physical effects are an important factor. Furthermore, under a weak ultrasonic physical effect at 490kHz, the inhibition effect when the internal substance moves to the corona from the micelle core is also important for estimating the retention of the internal substance by the micelle. In addition, we investigated the effects of thermal stimulation on DDR at several environmental temperatures. The internal dye was gradually released from the micelle when the environmental temperature was greater than 303K. Thus, appropriate design of external stimulation enables controlling not only the amount of effluence but also the release rate of the internal dye from the micelle.

Study on Noise Reduction of Suction Machine with Complicated Piping System by Use of Side Branch

Study on Noise Reduction of Suction Machine with Complicated Piping System by Use of Side Branch

원전 엘보우의 성능기반 안전여유도 분석

The piping systems in nuclear power plant are composed of various typed pipes such as straight, elbow pipe, branch and reducer etc. The elbow is connected from straight pipe to another pipes in order to establish the complicated piping system. Elbow is one of very important components considering management of wall thinning degradation. It is however applied by various loads such as system pressure, earthquake, postulated break loading and many transient loads, which provoke simply the internal pressure, bending and torsional stress. In this study, firstly pipes in the secondary system of the nuclear power plant are classified as pipe size and type for selecting the investigating range. Next, a large number of finite element analysis considering the all typed dimensions of commercial pipe has been performed to find out the behavior of TES(twice elastic slop) plastic load of elbows, which is based on evaluation of the structural safety factor. Finally performance based structural safety factor was investigated comparing with maximum allowable load by construction code.

Design of Magnetic Wheels and Drive Motor in Pipe-Surface Inspection Robot

We develop a robot that can automatically inspect pipes from the outside of the complicated piping in oil plants, etc. Our robots move by means of magnetic wheels. The natural rubber is used to generate friction against the piping. The robot consists of a lift part, a drive part, a motor for lifting a drive part, and a motor for driving a magnetic wheel. The drive part rises and descends through the rack gear when the motor installed in the lift part turns. The robot composed of three connected units is able to move along the horizontal piping, move along the lower side of straight piping, rise along vertical piping, and traverse a flange connecting two pipes, while holding the stability of the robot's posture. Next, we derive the adhesion condition suitable to horizontal/vertical pipes, the condition to detach from the piping, and the degree of adhesion of the magnetic wheel. Then we measure the power of the lift motor necessary for the robot to part from the piping, and we select the driving motor for rising along the vertical piping.

129 サイドブランチ型消音器による複雑配管を有する吸引機の低騒音化に関する研究(騒音・振動の解析・改善(3),騒音・振動評価・改善技術)

129 サイドブランチ型消音器による複雑配管を有する吸引機の低騒音化に関する研究(騒音・振動の解析・改善(3),騒音・振動評価・改善技術)

Model reduction for parametric instability analysis in shells conveying fluid

Flexible pipes conveying fluid are often subjected to parametric excitation due to time-periodic flow fluctuations. Such systems are known to exhibit complex instability phenomena such as divergence and coupled-mode flutter. Investigators have typically used weighted residual techniques, to reduce the continuous system model into a discrete model, based on approximation functions with global support, for carrying out stability analysis. While this approach is useful for straight pipes, modelling based on FEM is needed for the study of complicated piping systems, where the approximation functions used are local in support. However, the size of the problem is now significantly larger and for computationally efficient stability analysis, model reduction is necessary. In this paper, model reduction techniques are developed for the analysis of parametric instability in flexible pipes conveying fluids under a mean pressure. It is shown that only those linear transformations which leave the original eigenvalues of the linear time invariant system unchanged are admissible. The numerical technique developed by Friedmann and Hammond (Int. J. Numer. Methods Eng. Efficient 11 (1997) 1117) is used for the stability analysis. One of the key research issues is to establish criteria for deciding the basis vectors essential for an accurate stability analysis. This paper examines this issue in detail and proposes new guidelines for their selection.

Implications of the Rosa/AP600 High- and Intermediate-Pressure Test Results

Westinghouse has submitted the new AP600 reactor design for certification under the U.S. Nuclear Regulatory Commission (NRC) regulations for standard designs. The NRC has performed confirmatory testing in the Rig of Safety Assessment (ROSA) - V Large-Scale Test Facility run by the Japan Atomic Energy Research Institute (JAERI). The ROSA/AP600 test results as provided by JAERI are reviewed in terms of their implications for the original technical concerns that were to be addressed by the testing program. Implications for computer code capabilities are also discussed. Since gravity-driven natural circulation flow in a complicated piping network was a key concern, the review concentrates on this aspect of the ROSA/AP600 test results. In particular, it looks at the possible effect of system interactions at high pressure and during early depressurization. It identifies those ROSA/AP600 test occurrences that point to processes that could delay automatic depressurization system initiation or in-containment reactor water storage tank injection. Since most of the tests run were small-break loss-of-coolant accidents (SBLOCAs), the review focusses on this type of scenario. A comparison of several SBLOCA tests is presented.

Fluid vibration in piping systems—A structural mechanics approach, II: Applications

In the companion paper (Part I), a general computational technique was developed for the study of uniaxial linear vibration of compressible fluids in piping systems. In the present paper (Part II), seven numerical examples demonstrate the application of the technique. In harmonic vibration, the applied matrix method is analogous to the stiffness method in structural mechanics. Forced harmonic and transient responses are studied. Eigenfrequencies and eigenmodes are calculated. Five examples are designed for verification purposes. One example models a more complicated piping system met with in practice. The required computing time and also the upper limit of problem size for the program SFVIBAT-DAMP are evaluated in the last example.

Computer aided piping design system using an object-oriented language.

A computer aided piping design system is developed using an object-oriented language "Smalltalk-80". The piping design process is characterized by trial-and-error treatments, to add or delete the piping elements or to change the piping diameter in the course of the design process so as to satisfy the design condition. In the system the piping elements are represented as the "object", based on the computer language Smalltalk-80, which results in 1) flexible node I building and easy modification, 2)easy simulation to determine the total head and flow rate in the piping, 3)graphical representation of the design model of the piping and interactive control of the design process by the designer. The system provides a flexible approach to handling the piping design. It is also ascertained that the system can easily be enlarged to more complicated piping systems.

Vibration of Piping Systems Containing a Moving Medium

The subject of vibration of piping components containing a moving medium has been studied extensively in the past three decades. Special attention has been paid on the instability of uniform and tapered tubes with various boundary conditions. On the other hand, very limited information is available for complex piping systems carrying a moving medium. This paper proposes a transfer matrix method for the vibration analysis of complicated piping networks involving bends, piping components of various diameters, and lumped masses such as valves with a moving medium. Closed-form transfer matrix for various piping elements incorporating the Coriolis effects are presented and discussion is made. The proposed approach is much more economical to use than the versatile finite element method. Moreover, it can be easily implemented in a microcomputer.

End seals with welded metallic bellows for centrifugal pumps

The standard types of end seals for rotating shafts are widely used and have good acceptance in various types of industries. However, in many cases it becomes necessary to use complex systems for cooling and supplying sealing fluid so that the end seals can function properly. The need for such systems arises because the secondary sealing elements in end seals are made from elastomers which can be used only within a specified temperature range (--50 to +I00~ As a result, it becomes necessary to shift from single to double end seals and, in case of high temperatures, even to use a built-in refrigerating system. Thus, end seals tend to require complicated piping and refrigeration systems, auxiliary pumps, and regulators. The cost of the seal and expenses on operation/maintenance increase sharply, while the reliability decreases.

Elasto-Plastic Vibration Analysis of Piping System

In order to meet the qualifications for design of piping with respect to the earthquake inputs which are required to consider increment of the intensity, earthquake resistant design will be required to consider a piping component behaving in both its elastic and plastic regions. The elasto-plastic vibration analysis of piping is extremely difficult to perform in a generalized form. So, a piping simple in configuration was used to find elasto-plastic properties when it was vibrated. Two methods were devised for approximate elasto-plastic vibration analysis of complicated piping structures considering the elasto-plastic properties obtained from the vibration tests using a piping simple in configurations: one using a modal analysis methods and the other using equivalent linear damping. Calculated results obtained by applying these methods were compared with experimental data for verification of validity of these methods.

The acoustic simulation and analysis of complicated reciprocating compressor piping systems, II: Program structure and applications

The main objectives of the investigation reported in this paper, Part II, and its companion paper, Part I, are (a) to provide a formulation, including the mean flow effects and suitable for digital computer automation, of the acoustics of complicated piping systems, and (b) to develop a comprehensive digital computer program for the simulation and analysis of complicated reciprocating compressor piping systems. In this paper, the digital computer program structure and applications of the program developed, written in Fortran IV, are described. It is concluded that the computer program is versatile and user-friendly. It is capable of providing a great deal of information from one set of input data, and is open-ended and modular for updating.

The acoustic simulation and analysis of complicated reciprocating compressor piping systems, I: Analysis technique and parameter matrices of acoustic elements

This paper describes the mathematical formulation, equations, and procedures employed in the development of a comprehensive digital computer program for acoustic simulation and analysis of large and complicated piping systems. The analysis technique used is the transfer matrix method in which the piping system, with or without multiple inputs and outputs, is represented by a combination of discrete acoustic elements interconnected to one another at two stations such that the acoustic pressure and volume velocity at one station are uniquely related to those at the other by a two-by-two parameter matrix. Parameter matrices of 19 acoustic elements are included in this paper. By making use of these parameter matrices and the analysis technique, any complicated practical reciprocating compressor piping system can be modelled or analyzed.

Study on Pulsations of Reciprocating Compressor Piping Systems : 2nd Report, Model Experiment of Natural Frequency

The paper deals with the experiment conducted for examining the calculation method of natural frequency of a complicated piping system connected to a reciprocating compressor, which is described in the preceding paper. Experiment is conducted on 5 cases such as (1) Helmholz's resonance chamber, (2) piping with different sections, (3) piping with 2 inflow lines, (4) piping with bypass line and (5) general complicated piping, which are chosen as the combination of typical examples of elements. Experimental models used are made of vinyl chloride and resonant frequency and vibration mode then are measured by exciting the piping from one end by the loud-speaker. The results of experiments very well coincide with those of calculation and ascertain the applicability of the calculation method of the natural frequency in the preceding paper.

Study on Pulsations of Reciprocating Compressor Piping Systems

As a part of the analysis of response of pulsation from a reciprocating compressor complicated piping system, calculation method of pulsation is proposed in this paper which is an extension of natural frequency calculation reported in the preceding paper. Experiment is also conducted in measuring pulsations on the discharge-line of a Diesel engine supercharging air compressor in order to compare with the calculation results. The calculated amplitude of vibration becomes larger in the vicinity of resonant frequency due to the elimination of damping force, but the vibration mode has a perfect coincidence with experiment. Results of both experiment and calculation coincide very well in the non-resonant region. Also assumption of the discharging velocity out of compressor is proved almost correct.